Method of making paper



Feb. 24, 1953 G- RICHTER vI-:T AL 2,629,295

METHOD OF MAKING PAPER Filed June 15, 1945 o FIG I FIG. 3. DISTRIBUTION or FIBER LENGTH IN m cHIPPEn Ano NoN-CHIPPED PULP SHEET @aan EFFECT of EEATING uPoN x "E THE sETTLING RATEor 4'u 90 E (,H'PPED PULP 60 CHIPPED PULP SHE/ vm A if E 7 if,

w NoN-c I m4 0'1 7' STOCK 5o /6 PUL'IPSBEEDEI u Room T L E w soo V zo E m Io o I 1.0 2.o 3.o 4.0 FIBER LENGTH IN mm.

z m ,14'55LowNE55 D u g T' Em 7o sLowNEss I u \3osLowNEss FIGAI vl s" slLowNEss `7' sLowNEss 1 4 B12162024 zza'szvae TIME or sET-rLING IN MINUTE:

soo

FIG. Z.

EFFECT of' SEATING uPoN THE sETTLING RATE or NoN-CHIPPED woon PULP 'loo 0.17. sTocK Room T GET-rus vowME In I LITER (1000 mI) cmmnn ml) I |00'l sLowNEss 30g 'sol sLovrvnEss \22"' slLovEs-s 5' Low Ess I 'LA I I GEORGE A. RICHTER IDO ROBERT H. MACCLAREN INVENTORS BY TIME or sETTLING IN MINUTES wc/ ATT NEYS Patented Feb. 24, 1953 2,629,295 METHOD F MAKING PAPER George A. Richter and Robert H. MacClaren, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application June 15, 1945, Serial No. 599,542

4 Claims. l

This invention relates to a process of making paper from wood pulp in which wood pulp sheet is cut while in dry form into chips having a width of ggd/64, inch, which chips are dispersed in Water and paper is formed from that dispersion.

Ordinarily in the making of paper, cellulose fibers are shortened by a Wet operation such as by treatment in the beater or Hollander, the Jordan, or both. Shortening of fiber under these conditions is unavoidably accompanied by a `partial hydration or gelling of the fiber. Hydration of the fiber gives effects which are frequently undesirable, particularly in most types of photographic paper, and therefore in prior practice in making those types of paper it has been necessary to compromise between the degree of cutting and the extent of ber hydration.

In previous cutting operations there has been no thought of displacing the wet shortening operations of paper making by this dry comminuting procedure. In many of those previous cases in which comminution has been carried out, the ber instead of merely being shortened has also been ground or macerated so that hydration of the fiber is not avoided.

@ne object of our invention is to prepare paper having a low across the machine Wet eX- pansion, and good iiatness. Another object of our invention is toprepare paper having good formation as evidenced by uniform translucency, Further objects of our invention will appear herein.

It is characteristic of many papers uponwetting, especiallyA on one side, that vcurling or cockling occurs. Such paper is not entirely suitable for wet processing or for use under humid conditions, as cockie of the paper may result. Our invention is adapted to accomplish a twofold purpose of providing paper having a minimum of wet expansion anda uniform formation or translucency throughout.

Chemical wood pulp as ordinarily prepared by the pulp manufacturer is sheet or pulp board, and the fibers are mostly in the direction in which' `the pulp sheet or board was laid down. 4We have found that if thispulp sheet or pulp board such as ordinarily employed as the starting material in paper-making processes, particularly that made up of the bers of coniferous Woods characterized by being longer than the ber of nonconiferous Wood, is cut across the machine direction of the pulp,` or in other words at right angles to a large proportion of the fibers `in the sheet, so that substantially all of the bers are reduced to a length in the form of a pulp` of not more than 3 mm. or 1/3 of an inch a paper may be prepared therefrom having highly desirable properties. `This is accomplished by first chipping `the pulp sheet into chips whose width is le-/ci of an inch, cutting across the machine direction of the pulp. This cut or chipped pulp is disintegrated and suspended in water so as to form a dispersion having a slowness of 5-100 seconds and a settling character such that a 0.1 per cent furnish settles to a volume of `pulp less than per cent of the original volume after 10 minutes of settling, and paper is made from that suspension. The paper obtained exhibits low across the machine wet expansion, good flatness, good resistance to curling; and good formation. l

After the pulp has been chipped, it must be dispersed to form an aqueous mass suitable for forming paper. This may be done in the beater in which the bed-plate is adjusted to produce the desired slowness Within the previously mentioned range. If the dry cutting or chipping results in sufficient shortened fibers to assure the slowness desired, no beating is necessary and, in fact, the cut fibers lmay-be dispersed without the use of either a `beater or a Jordan, such as in a pro--` peller-type mixer. If, however, more fiber shortening is desirable, this may be accomplished by processing through a Jordan or in a beater with a minimum of hydration so that the resulting pulp slowness is between 5 and 100 seconds, such as 18, 40, 55, or 83 seconds.

In the accompanying drawing, Figures 1 and 2 are graphs comparing the characteristics of beaten pulp' prepared in accordance with our invention with beaten pulp which had not been previously chipped. These graphs illustrate the height of the settled pulp after settling as occurred with pulps of various slownesses, Figure 1 being directed to pulp which had been chipped as described herein andthen beaten, and Figure 2 being directed to the settling heights of pulp suspensions in which pulp sheet has been beaten up without first chipping. It will be seen from these curves that the settled height and settled volume of a chipped pulp having a slowness of` less than seconds is less than 20 per cent of the original height or volume of the pulp dispersion after 10 minutes of settling. The pulp dispersion employedwas one liter in volume and of 0.1 per cent concentration and after settling for 10 minutes, the dispersion of the pulp,Y

having slowness of less than 100vseoonds, is lessthan 20 per cent of the original volume ofoneliter.-l

Figure 3 is a graph in which the fiber length of the suspended fibers in millimeters is plotted Y against the percentage of the total weighed fiber l 4 viewed by transmitted light, is obtained and the cloudy, mottled effect often seen in papers is avoided. Paper of good formation (that is hav-- ing a uniform translucency) is especially useful' for photographic purposes.

One of the advantages of our invention is that the speeds of paper machines may be increased of the fibers present are less than 3 mms. and

the greater part of the bers therein are less than 2 mms. in length. The proportions of the fibers of various lengths are determined by dispersing the pulp in water and determining the number of fibers of the various lengths by microscopic examination. In this way the number of iibers within the given lengths may be easily determined.

Figure 4 is a drawing of a Williams freeness Y tester which is employed for determining the slowness of the pulp dispersions. This tester consists of a graduated cylinder graduated from 0 to 1,000 mls. so arranged that the liquid therefrom must pass through a screen in running a freeness test. The screen employed is one having a '78 x 56 wire mesh screen. The tes-ter is also fitted with a ball check to avoid formation ofV vacuum below the screen so that uniform draining of water from a pulp dispersion being tested is accomplished. The use of the Williams freeness tester in determining the slowness of a pulp dispersion will be described hereinafter.

Paper obtained in accordance with our invention with a stearic acid sizing has an.across the machine wet expansion of less thanrl per cent, this value vusually being within the range of 1.3 to 1.5 per cent. With paper prepared from a pulp which has been shortened only in the wet state by beating or jordanning, this paper with a stearic acid sizing has an across the machine wet expansion on the order of 3 per cent or possibly more. The papers referred to are those beater sized with sodium stearate and alum in accordance with the disclosure of U. S. 'Patent No.V

1,840,399 of Gerould T. Lane. Instead of stearic acid, the paper may be sized with rosin and a similar difference in wet expansion will be ob- Y served between a paper prepared in accordance with ourV invention and one prepared in the customary manner. Y

It is'possible to very considerably Vreducegthe wet expansion of. a paper preparedfrom a pulp which has'been shortened by beating, by bcater sizing the pulp with a melamine-monoureidformaldehyde sizing or with a melamine-formab dehyde sizing as taught in U. S. Patent No.

2,548,513 of Boughton. In fact, paper may be prepared by this means having a wet` expansion less than paper prepared inv accordance with our invention which has not been sized with a wetresistance-imparting sizing material.V However,

sistance-imparting sizing material such as wefstrength-.imparting melamine-formaldehyde,resin or melamine-monoureid-folmaldehyde resin exhibits a substantial decrease in across the ma-j chine wet; expansion over that ofpaper, vsimilarly sized,' prepared from a pulp which hasY been shortened by beating. Y

' paper prepared in accordance with our invention 1 whichY paper has embodied therein a wet-res` Vslowness will be equalled or exceeded in paper' formation by a pulp of 19 seconds slowness prepared in accordance with our invention. It is"- preferred that the pulp in accordance with our' invention when ready for the machine have a slowness of 5-40 seconds, for example 8, 14, 26,- 3l or 37 seconds.

The forming of the pulp-board chips which are employed for making paper, in accordance with our invention, may be accomplished by cutting the pulp board with blades or chipping' knives, such as aixed to a rotating member which is rotating at highest speed. 1t is desirabie to have a bed plate or other metal surface to facilitate the chipping opera-tion, it being preferable that the` chipping knives be so adjusted that there is a small clearance between the knives and the bed plate. The speed of feeding the pulp board to the rotating cutting member should be adjusted depending upon the speed at which the rotating cutting member is operated so as to give chips having a width or not more than of an inch, preferably approximately he, of an inch. For convenience the chips may be of a length of lAiinches. The pulp board or puip sheet from which the chips will be formed may be any suitable commercial form of felted pulp. The sheet may be of any width capable of operation in the machine. The thickness of pulp board which is moved toward the cutting blades should be such that these blades will quickly and satisfactorily cut and/or tear the widths therefrom. Ordinarily, it is desirable that this thickness of the pulp board be from about is to about 1/4 of an inch. If the pulp sheet which is used is about als of anV inch in thickness, obviouslyY it willrbe desirable to run only three or four thicknesses of the particular pulp sheet vthrough at the same time. Due to the stiffness of the pulp sheet or pulp board which-is cut while in dry condition,

Vthere is no need for any Ycontacting of the cut'- ployed ior the starting material for our invention is of iibers extracted. from coniferousV-wood,

Y such as spruce, hemlock, fir or pine by a cooking or digesting operation.

' In the'carry-ing out of the cutting operation,

it is the best practice to operate so that a good,

clean cut is obtained. In the case of some pulps additional drying of the pulp sheet-is'desirablel 'Y Y 'to get a clean cut. For instance, itis often desirable with some typesY of` pulp to dry it down Y to a moisture content of less than 1% forthebest cutting.V In the case'of other types of pulp, cleanV cutting may be obtained 4without additional drying. As a general rule, kraft pulp is out better when bone dry while sulte pulp need not be dried beyond air-dry condition, for instance 5-10 per cent moisture content, for good cu-tting to occur.

We use sheet pulp in which the bers primarily run lengthwise of the sheet so that the fibers are shortened. Pulp sheets as ordinarily prepared on the cylinder machine are laid down with the fibers lengthwise and these sheets are eminently suited for use in our process.

After the dry cutting of the pulp sheet has occurred, the material being obtained in the form of chips, this material is then disintegrated in water to form an aqueous suspension of the pulp. This dispersion of the pulp in water may be accomplished by various means, such as, for instance, by passing the water containing the pulp chips through a pump of a type which will disintegrate the chips, in a beater and/or Jordan providing the pulp obtained has a slowness of 5-100 seconds, preferably 5-40 seconds, and a settling rate as previously specified.

In the preparation of paper in accordance with our invention a sizing material is preferably incorporated into the pulp dispersion at some time prior to the time when it is formed out onto the wire of the paper machine.` For instance, the sizing material may be rosin, hydrogenated rosin or stearic acid, which has been saponined such as with caustic soda. Ordinarily, the size may be prepared from the rosin, hydrogenated rosin or stearic acid by treating with 1/3 of its Weight of caustic soda. The soap thus formed can be used in any dilution desired.

When the sizing is added to the pulp dispersion there is also added thereto some acidic material, the most commonly used material for this purpose being alum. Other acidic materials rather than alum may be used such as aluminum chloride, sulfuric acid, hydrochloric acid or the like.

In addition to or instead of the above-mentioned sizing materials the paper may be sized by incorporating in the pulp dispersion a melamineformaldehyde resin or a melamine-monoureidformaldehyde resin. For instance, a hydrochloric acid solution of a melamine-formaldehyde resin having Wet strengthimparting properties as described in U. Si. Patent No. 2,345,543 may be added to` the pulp dispersion and thoroughly mixed therein prior to forming paper therefrom on the wire of the paper machine. If desired, a melamine-moncureid-iornialdehyde resin having wet-strength-imparting properties may be added to the pulp dispersion prior to paper formation.

After the pulp has been throughly disintegrated so as to form an aqueous suspension and a sizing material has been incorporated therein, it is formed onto the wire of the paper machine `so as to form a hard, dense paper comparable in character as to denseness, or even more dense, than paper ordinarily prepared. The paper which is prepared in accordance with our invention should preferably have a weight of 3 to 6 pounds per 1,000 square feet per 1/1000 of an inch thickness. Due to the fact that the pulp in accordance with our invention occupies less volume upon settling than wet-shortened pulp fibers, the obtaining of a dense sheet is not difficult. Paper in accordance with our invention is especially suitable for use as the base of photographic paper.

As the coating compositions in making photographic papers are aqueous, paper which is not affected by wetting and then drying is of value for this purpose.

Photographic papers in use are subjected to aqueous baths such as in developing, printing and A pulp sheet of high alpha sulte pulp obtained from Western Hemlock Wood by digesting and refining, is chipped by running a roll of the pulp `sheet longitudinally through a chipping mechanism which sharply shears strips of approximately t inch width and 1% inch long therefrom, thus cutting across the bers of the sheet. Six hundred pounds of this chipped pulp are suspended in 1100 gallons of water in the beater, the pulp mixture being mixed with 10 pounds of sodium stearate size, 45 pounds of corn starch and 15 pounds of aluminum sulfate, the materials being added to the water in the beater in the order given. After the beating takes place for only a suicient time to disperse the pulp in the water and to condition the pulp for forming paper, it is transferred to the paper machine, such as through a Jordan in which the knives are of suiiicient sharpness and of proper design such that excessive hydration does not occur. The resultant stock having a slowness of 30 seconds is then processed over the paper machine in the conventional manner, toform a dense sheet of paper. The resulting paper shows good formation and less across the machine wet expansion than is exhibited by corresponding paper prepared from the pulp beaten or jordanned to shorten the bers rather than by a dry chipping operation.

Example 2 A pulp sheet from kraft high alpha pulp obtained 'from Northeastern Spruce wood `by digesting and refining is chipped by running a roll of the pulp sheet longitudinally through a chipping mechanism which sharply shears strips of approximately of an inch `width and 3A inch length therefrom, thus cutting across the fibers of the sheet. Six hundred pounds of this chipped pulp are suspended in D gallons of Water in the beater avoiding abnormal hydration. The #pulp suspension is mixed with the following materials added in the order given:

5.6 pounds of sodium aluminate 9.6 pounds of sodium stearato 3.0 pounds of gelatin 45.0 pounds of cooked corn starch 4.5 gallons of hydrochloric acid (24 The beating is only continued for a suihcient time to assure good dispersion of the pulp and to condition the pulp for the formation of paper. A hydrochloric acid solution of an acid-aged melamine-formaldehyde re-sin as described in Wohnsiedler Patent No. `2,345,543 is then added to the stock in an amount that the `resin constitutes 1,/2 per cent of the weight of the bone dry pulp. i

The resultant stock having a slowness within the range `of 25 seconds is then processed over a paper .machine in the conventional manner. A

, paper of good formation is obtained having across the machine Wet expansion superior to Vhydrogenated rosin with approximately ance with the following procedure: One poi bonedry pulpris suspended pension it may be diluted cc. sample of slush Y to 1G60 cc. with water, all at a temperature of 32.5 C. ,(TOUYF.) Waterhaving the saine tem-V that of papers of. like. liirlrlin which heating is.

depehzzled' upon, rather than dry chipping for shortening of the fibers of the pulp.

Example 3- is added to the pulp dispersion approximately 1% of hydrogenated rosin size and approximately 1% of aluminum sulfate, the percentages being based upon the bone dry weight of the pulp. The hydrogenated rosin size is prepared 'by saponifying 1/s its weight of caustic soda. After the pulp has been thoroughly dispersed. inthe `water forming a dis persion of 2u seconds and is in condition for forining paper, it is passed to the paper machine pref erably through a Jordan in which the 1Knives have been so adjusted that little or no hydration oc.- curs therein. The resultant stock is then procassed over the paper machine in the conventional.

manner.

Example 4 Paper is prepared in the same manner as in Example 2 except that a melaniinemonoureid formaldehyde resin in solution in hydrochloric Iid is added to the stock in an. amount 1/2 it of the weight or" the hone dry Ipulp instead of the melamine-formaldehyde resin employed therein. The paper Ysheet is made on the machine in the customary manner.

Example 5 Vwhich is less affected by processing solutions and washing than a corresponding paper prepared in the manner of the prior art.

The wel; expansion of paper and its shrinkage upon drying is determined by a well known instrument Vknown as a Schepper Apparatus for Testing the Expansion of 7:Paper under the Iniuence of Moisture manufactured by Louis Schepper ci Leipzig, in which changes in dimene sions of the paper cause a pointer to move over a graduated scale. Further description of the ap- .Y

paratus for measuring the expansion and contraction ci paper is given in an article by Griiiin in the Paper Trade Journal or August 4, i927.

The slowness of paper .pulp as used herein is determined with aY Williams reeness Vtester as illustrated in Figure fi of the drawing in accord- Vof in 20 pounds of water F. in device m which the fiber is brought Vinto suspension without any hydration occurring'. A Valley beater may be employed for Y thispurpcse without using any weight on the bed- Y Where the' pulp is already in susto correspond to a suspension of 1 pound` of iiber'in 2) liters or water used directyv in the following test: A le-45 as prepared above, is diluted plate lever;

8V perature is added `to the Williams .reeness tester up to the 0 cc. mark. and then the 1000'cc. mass of water and ber is poured into the graduated cylinder of the tester. As soon as the air bubbles (formed by the pouring) have risen, the drainage valve is turned and the time interval for the drainage of the 1G00 cc. of water from the sus pended ber is obtained. rFhis value in seconds is the slowness of the pulp.

The settling test is carried out by taking a dispersion of pulp in water, diluting with water sufficiently to obtain a stock or furnish of 0.1 per cent concentration, placing one liter of that pulp suspension in a oneliter graduate and closer/ineT the settled volume of the pulp at selected time intervals, for instance, every two or three minutes.V

The selectionV of this time interval will depend upon the rapidity at which the curve is changing direction at any particular point. After these observations are taken, curves are then made from. the data obtained therefrom as illustrated by Figures 1 and 2 of the drawing attached hereto.

It is to be understood that our invention is primarily directed to low wet expansion paper and its preparation by means of the chipped pulp described herein. A low wet expansion paper may be prepared in which chipped pulp is not 106% of the pulp used, i. e., some nonechi-pped pulp may be mixed therewith without impairing the low wet expansion imparting properties of the chipped pulp. Such a modification is considered. as being Within'the scope of our invention as defined by the appended claims.

We claim:

l. A method of preparing paper which consists in transversely cutting a dry sheet of coniferous wood pulp, the fibers of which mainly run lengthwise, at intervals of approximately tlf of an inch, thereby forming chips or that approximate width, agitating the chips in water to disperse the pulp fibers therein and to form a suspension having a slowness of 5-100 seconds by the Williams reeness test, providing the suspension with sizing chemicals and preparing paper from the pulp suspension while maintaining the slowness within 5-100 seconds whereby paper of good flatness, low wet expansionY and uniform formation is obtained.

.2. A method of preparing paper which consists in transversely cuttinga dry sheet of co niferous wood pulp, the fibers of which mainly run lengthwise, at intervals of approximately al; of an inch, thereby forming chips of that approximate width, agitating the chips in water to disperse the pulp fibers therein and to formV a suspension having a slowness of 5l0 secondsV suspension while maintaining the slowness within 57-100 seconds whereby paper or" good iiatness, low Wet expansion and uniform formation is obtained. Y

3. A method of preparing paper which con'- sists in transversely cutting a dry sheet of coniferous wood pulp, the bersof which mainly run lengthwise, at intervals of approximately :Je of an inch, thereby forming chips of that ap" proximate width'agitating thej chips inV water to disperse the pulp fibers therein and to form a suspension having a slowness of 5-100 seconds by the Williams freeness test, providing the suspension with sodium stearato paper size' and preparing vrpaper from the pulp suspension while maintaining the slowness within 5-100 seconds whereby paper of good atness, low wet expansion and uniform formation is obtained.

4. A method of preparing paper which consists in transversely cutting a dry sheet of coniferous wood pulp, the bers of which mainly run lengthwise, `at intervals of approximately 12 of an inch, thereby forming chips of that approximate Width, agitaing the chips in water to disperse the pulp fibers therein and 4to form a suspension having a slowness of 5-100 seconds by rthe Williams freeness test, providing the suspension with hydrogenated rosin paper size and preparing paper from the pulp suspension while maintaining the slowness within 5-100 seconds whereby paper of good atness, low Wet expan' sion and uni-form formation is obtained.

GEORGE A. RICHTER. ROBERT H. MACCLAREN.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,050,367 Lewthwate Jan. 14, 1913 1,417,961 Williams May 30, 1922 1,716,006 Rinman June 4, 1929 1,786,538 Johnson Dec. 30, 1930 1,826,825 Rich-ter et al. Oct. 13, 1931 Number Name Date 1,829,763 Schorger Nov. 3, 1931 1,838,614 French Dec. 219, 1931 1,840,399 Lane Jan. 12, 1932 1,842,689 Richter Jan. 26, 1932 1,944,906 Schwartz Jan. 30, 1934 1,959,965 Richter May 22, 1934 1,980,881 Schur Nov. 13, 1934 2,028,080 Stern Jan. 14, 1936 2,054,301 Richter Sept. 15, 1936 12,065,395 Richter Dec. 22, 1936 2,345,543 Wohnsiedler et al. Mar. 28, 1944 FOREIGN PATENTS l5 Number Country Date 210,166 Great Britain Jan. 23, 1924 OTHER REFERENCES Manufacture of Pulp and Paper, 3rd ed., vol.

lo III, sec. 1, p. 42 and sec. 8, pages 22 to 26 (1937),

Paper Trade Journal, Dec. 24, 1942, pages 40 to 42.

Pulp and Paper Manufacture, vol. 1, pages 941 to 962 (1950), published by McGraw-Hill, N. Y. 

1. A METHOD OF PREPARING PAPER WHICH CONSISTS IN TRANSVERSELY CUTTING A DRY SHEET OF CONIFEROUS WOOD PULP, THE FIBERS OF WHICH MAINLY RUN LENGTHWISE, AT INTERVALS OF APPROXIMATELY 1/32 OF AN INCH, THEREBY FORMING CHIPS OF THE APPROXIMATE WIDTH, AGITATING THE CHIPS IN WATER TO DISPERSE THE PULP FIBERS THEREIN AND TO FROM A SUSPENSION HAVING A SLOWNESS OF 5-100 SECONDS BY THE WILLIAMS FREENESS TEST; PROVIDING THE SUSPENSION WITH SIZING CHEMICALS AND PREPARING PAPER FROM THE PULP SUSPENSION WHILE MAINTAINING THE SLOWNESS WITHIN 5-100 SECONDS WHEREBY PAPER OF GOOD FLATNESS, LOW WET EXPANSION AND UNIFORMLY FORMATION IS OBTAINED. 